A method for identifying damage to a friction clutch arranged between a drive unit and a gearbox is known from DE 10 2005 061 080 A1. Here, the damage is derived from individual damage values determined on the basis of the frictional power input into the friction clutch. If the determined individual damage values exceed a threshold, the friction clutch is evaluated as being damaged.
Such monitoring systems are used in particular for reliable, economical and comfortable operation. For example, these monitoring systems are used in dual clutch gearboxes in which the friction clutches are subject to intense loading, in particular, at high load and during overlapping shifts. In this way it is sought to reliably detect during operation whether one or both friction clutches is not reliably transmitting the torque to be transmitted and has, for example, increased slip at the presently applied torque of the drive unit.
In new friction clutches, which have not yet been run in, relatively low friction coefficients are obtained because the friction pairing of friction linings of the clutch disk and the counterpart friction surfaces of the friction clutch has not yet been run in. This may be attributed, inter alia, to the fact that the friction linings, which are still relatively uneven after manufacture, have, on a microscopic scale, only a small contact area with the counterpart friction surfaces of the pressure plate or of the counterpart pressure plate. With progressive run-in duration, the unevenesses of the friction linings and also the counterpart friction surfaces are worn away and a larger effective friction surface is formed. This leads to higher friction coefficients, which are used as a basis for the evaluation of the friction clutch as being functionally capable.
Friction clutches which have not yet been run in can lead to over-revving of the drive unit at the torque of the drive unit applied under normal conditions and can be identified as worn by an evaluation routine. This can erroneously lead to a complaint and an associated exchange of the friction clutch in question, or, in the case of a dual clutch of a dual clutch gearbox, to the complete exchange of the dual clutch.